test_external: Extract common logic for "hit rate limits" tests.
test_external: Extract common logic for "hit rate limits" tests.

rht/zulip,andersk/zulip,punchagan/zulip,eeshangarg/zulip,hackerkid/zulip,rht/zulip,zulip/zulip,rht/zulip,kou/zulip,hackerkid/zulip,eeshangarg/zulip,kou/zulip,zulip/zulip,eeshangarg/zulip,kou/zulip,hackerkid/zulip,eeshangarg/zulip,kou/zulip,rht/zulip,punchagan/zulip,hackerkid/zulip,andersk/zulip,kou/zulip,punchagan/zulip,andersk/zulip,andersk/zulip,punchagan/zulip,hackerkid/zulip,zulip/zulip,rht/zulip,rht/zulip,rht/zulip,zulip/zulip,eeshangarg/zulip,hackerkid/zulip,punchagan/zulip,zulip/zulip,andersk/zulip,kou/zulip,zulip/zulip,zulip/zulip,hackerkid/zulip,kou/zulip,eeshangarg/zulip,punchagan/zulip,eeshangarg/zulip,punchagan/zulip,andersk/zulip,andersk/zulip